Islamabad: Thousands of supporters of a fiery Pakistani cleric who has been calling for election reforms descended on Monday onto the capital, as security officials girded for mass rallies by a movement that has virtually overnight become a powerful but still mysterious force on the political scene.

The dramatic entry into Pakistani politics of Tahir-ul-Qadri, a preacher who until recently lived abroad in Canada and had only a modest local following, has galvanised supporters looking for reforms but worried detractors who fear he’ll derail upcoming elections.

Also on Monday, thousands of Shiites finally ended a three-day long protest in the southwestern city of Quetta in which they demanded better security following an attack that killed 86 people. They had blocked a main road with dozens of the victims’ coffins, and finally agreed to bury their relatives after Pakistan’s leaders dismissed the government of surrounding Balochistan province.

The national government is also worried about security in Islamabad in advance of Qadri’s protest. Thousands of police have been deployed in the city, and officers in riot gear are manning the main roads and streets. Authorities used shipping containers to block off the part of Islamabad where most government offices and embassies are located.

About 15,000 of Qadri’s supporters left on Sunday in hundreds of vehicles from the eastern city of Lahore, where the headquarters of his Minhaj-ul-Quran organization are located. They are expected to arrive in Islamabad later on Monday, as more supporters join the rally along the way.